Cellular mobile telephone services are currently one of the most rapidly expanding types of communication services. They have been in operation in the continental United States for nearly a decade and have been offered in many other parts of the world for several years.
Whereas cellular mobile telephone services were once limited to relatively small geographic home areas, they have since evolved to permit expanded service across state and national boundaries through "roaming" agreements. This expansion has served the commercial objectives of mobile telephone service providers by providing roaming mobile subscribers the ability to freely and quickly automatically originate and receive telephone calls from other fixed or mobile stations in the network. At the same time, however, this service expansion has also placed service providers at risk of theft due to the inherent drawbacks in conventional validation schemes.
Consider, for example, cellular mobile telephone systems which provide services to cellular sub-scriber who travel or "roam" away from their home markets. Before initiating cellular service to the roaming user, a serving carrier validates the subscriber's Mobile Identification Number (MIN) and Electronic Serial Number (ESN) to verify that these numbers are in good standing. More specifically, when a subscriber first enters a roaming market or "powers up" her cellular telephone in a roaming market, her unique MIN and ESN are transmitted to a serving carrier of the serving market. These numbers identify to the serving carrier that the subscriber whose access codes have been transmitted is not a local subscriber. Utilizing an IS-41 network, the server therefore requests registration data from the subscriber's home carrier which corresponds to the received MIN/ESN. This registration data is delivered via the IS-41 network back to the serving market to provide information to the serving carrier regarding the subscriber's call features and restrictions and to enable the carrier to make a decision whether or not to provide service.
As readily seen, the system validates that a particular MIN/ESN is entitled to roaming privileges. It fails, however, to determine whether the specific user or, for that matter, the phone itself are in fact legitimate. In short, prior art mobile telephone systems validate access codes only--not subscribers. Once the transmitted access codes have been verified, the prior art systems merely assume that the true subscriber is the user who is requesting access in the roaming market.
Unfortunately, in practice, this assumption has proven false. In recent years, there has been a dramatic increase in roamer "clone" fraud. That is, unscrupulous users who improperly obtain the access codes of legitimate users and thus "clone" their identities for the purpose of committing fraud on the service provider.
One known system for preventing and detecting cloning fraud is provided by GTE Telecommunication Services, Inc. (GTE TSI). GTE TSI provides a clearing-house validation service by maintaining a "positive" database of valid subscriber MIN/ESNs and a "negative" database of invalid subscriber MIN/ESNs. When a call is received by the GTE TSI system, a lookup is performed against the positive and negative databases to determine if the MIN/ESN combination is valid. If not, the MIN/ESN is entered into the negative database. This system, however, only validates MIN/ESN combinations, and does not know which portion of the combination is invalid. Furthermore, this system only validates data after a call is placed, not before.
Another known system for preventing cellular fraud is disclosed in U.S. Pat. No. 5,335,278, issued to Matchett et al. This system is a refinement of the GTE TSI-type system described above in which each cellular network carrier transmits its positive and negative database to a central source. The central source than broadcasts or transmits this information to each cellular network carrier so that each cellular network carrier can determine if a roamer request for service is from a valid, currently authorized mobile unit before cellular telephone service is provided by the visited cellular network. This system, however, is a paid-for service in which the service provider performs the validation service for the home cellular carrier for a fee.
Another known system utilized in both the IS-41 network and the X.25 network comprises a clearing-house that provides the home carrier with the capability of ensuring that their roaming MINs are being used by legitimate subscribers. When a roaming caller attempts to register, the serving market switch sends a request to the home carrier switch to determine if the MIN/ESN is valid and what kind of service they have subscribed to. At the same time, the clearinghouse monitors the home carrier and serving market identification codes to determine if this home carrier/serving market combination needs to be monitored for the home carrier. If so, the clearinghouse then determines if the MIN/ESN is valid. If the MIN/ESN is not valid, then the clearing-house directs the serving carrier to forward all calls from the MIN/ESN to the clearinghouse while they are in the serving market. This system requires the customer to be forwarded to an unknown third party service, rather than their own customer service. Furthermore, this system monitors only the home carrier/serving market combinations chosen by the home carrier. Therefore, if a user does not satisfy the requirements of customer service, the user can Roam to another serving location that the clearinghouse has not been instructed to monitor.
Thus, there exists a need for a simple, fast, and reliable system for detecting and preventing mobile roaming fraud by any mobile carrier at all times.